Figure 1.

Measurements and results of virtual dual-energy processing for a material phantom. (A) Photography of the sample consisting of 6 different solid or liquid materials. From the reconstructed attenuation (B) and phase-contrast (C) data an effective interaction energy of $E_{\mathrm{eff}}^{\mathrm{\mu },\mathrm{\delta }}=\mathrm{24.6,}23.8\mathrm{keV}$ was assigned via the literature value for the linear attenuation coefficient and the refractive index decrement of PMMA. The effective atomic number map (D) shows the distribution of Z_eff ≈ 6.25 for Nylon to Z_eff ≈ 7.99 for iodine. The quantitative iodine map (E) shows positive values of [I] ≈ 4.6 mg/ml only for the iodine solution. The virtual non-contrast image (F) is the conventional attenuation image where the identified iodine containing pixels are replaced with the attenuation value of water. The virtual monoenergetic image at $E_1^{\mathrm{VMI}}=25\mathrm{keV}$ (G) looks very similar to the conventional attenuation image. For the higher energies (H,I), the contribution of the electron density increases and the virtual monoenergetic image at $E_{\mathrm{3}}^{\mathrm{VMI}}=120\mathrm{keV}$ looks very similar to the electron density image (which is simply proportional to the refractive index decrement image).